Improve UDTs and Tuples documentation
Improve UDTs and Tuples documentation

patch by Fábio Ueno; reviewed by Benedict Elliott Smith and Benjamin Lerer
for CASSANDRA-16117

adelapena/cassandra,apache/cassandra,szhou1234/cassandra,mshuler/cassandra,thelastpickle/cassandra,blerer/cassandra,driftx/cassandra,tjake/cassandra,thelastpickle/cassandra,adejanovski/cassandra,mike-tr-adamson/cassandra,blerer/cassandra,blambov/cassandra,bdeggleston/cassandra,michaelsembwever/cassandra,jrwest/cassandra,adejanovski/cassandra,beobal/cassandra,tjake/cassandra,blerer/cassandra,apache/cassandra,mike-tr-adamson/cassandra,adejanovski/cassandra,jrwest/cassandra,driftx/cassandra,mike-tr-adamson/cassandra,blerer/cassandra,pauloricardomg/cassandra,belliottsmith/cassandra,instaclustr/cassandra,mshuler/cassandra,blambov/cassandra,thelastpickle/cassandra,adelapena/cassandra,tjake/cassandra,beobal/cassandra,michaelsembwever/cassandra,instaclustr/cassandra,tjake/cassandra,mshuler/cassandra,michaelsembwever/cassandra,beobal/cassandra,blambov/cassandra,szhou1234/cassandra,adelapena/cassandra,szhou1234/cassandra,jrwest/cassandra,instaclustr/cassandra,mshuler/cassandra,mike-tr-adamson/cassandra,belliottsmith/cassandra,bdeggleston/cassandra,instaclustr/cassandra,thelastpickle/cassandra,beobal/cassandra,blambov/cassandra,apache/cassandra,apache/cassandra,jrwest/cassandra,pauloricardomg/cassandra,szhou1234/cassandra,bdeggleston/cassandra,pauloricardomg/cassandra,bdeggleston/cassandra,belliottsmith/cassandra,belliottsmith/cassandra,pauloricardomg/cassandra,michaelsembwever/cassandra,adelapena/cassandra,driftx/cassandra,driftx/cassandra